The present invention relates to a convenient, high yield process for sulfating alcohols. The process of the present invention is adaptable to sulfating a wide range of alcohols including the hydroxyl unit which terminates a polyalkoxylate moiety which are prevalent in the area of surfactants, inter alia, alkyl ethoxy sulfates. The sulfation process of the present invention can be used to sulfate poly-alcohols or amino alcohols, the latter which can serve to provide a key element necessary for sulfation.
The most common process for manufacturing alcohol sulfates encompasses falling film reaction techniques. This process most often uses SO3 as the sulfation reagent to sulfate the parent alcohol. While this technique is well known in the industry, it requires specialized equipment and can produce unwanted side products. In particular, dioxane is usually produced by side reactions when ethoxylated materials are involved. Other complications in falling film sulfation can lead to salt by-products, over-sulfation and color/odor issues. In addition, falling film reactors are not easily adapted for use in sulfating alcohols wherein the desired product is a non-aqueous, high active composition due to the industry practice of using aqueous base such as sodium hydroxide to neutralize the acidic initial sulfation product.
There is therefore a long felt need to provide a convenient process for controllably sulfating hydroxy units without the need for specialized equipment. There is also a long felt need for a process for sulfating alcohols to produce a non-aqueous, high active product. In addition, there is a long felt need for a alcohol sulfation process which minimizes unwanted side reactions and salts. In addition, there is a long felt need to controllably sulfate amino alcohols, the product of which process yields zwitterionic materials, for example, surfactants.
The present invention meets the aforementioned needs in that it has been surprisingly discovered that hydroxyl moieties can be controllably sulfated by the trans-sulfation process described herein. In an important embodiment of the present invention, a portion of the substrate to be sulfated, can serve as a reagent participating in the process as an essential element or component, for example, as a source of amino moiety. The sulfation process of the present invention allows the formulator to introduce into the molecule to be sulfated a pre-determined degree of sulfation. In addition, the reagents which are required to perform the process of the present invention minimize unwanted by-products, inter alia, inorganic salt by-products due to neutralization, or side products, inter alia, dioxane and other cyclic ethers. The process of the present invention can be conducted in standard chemical reaction vessels instead of specialized equipment such as falling film reactors. A further advantage of the present process is the ability to produce anhydrous, high active sulfated alcohols.
The first object of the present invention relates to a sulfation process comprising the steps of:
a) reacting a tertiary amine with a sulfation precursor having the formula: 
wherein R1 is C1-C22 alkyl, C7-C22 alkylenearyl, and mixtures thereof; to form an admixture comprising a quaternized amine and a sulfating species; and
b) reacting a hydroxyl species with said admixture to form a sulfated hydroxyl species.
A further aspect of the present invention relates to a trans-sulfation process comprising the steps of:
a) reacting n equivalents of an amine moiety with n equivalents of a sulfation precursor to form n equivalents of a sulfating species; and
b) reacting said n equivalents of a sulfating species with a substrate having n hydroxyl moieties to form a compound having n sulfated hydroxyl moieties.
The present invention also relates to a trans-sulfation process comprising the steps of:
a) reacting n equivalents of a tertiary amine moiety with n equivalents of a sulfation precursor to form n equivalents of a sulfating species; and
b) reacting said n equivalents of a sulfating species with a substrate having m equivalents of hydroxyl moieties to form a compound having up to n sulfated hydroxyl moieties.
A yet further aspect of the present invention relates to a trans-sulfation process comprising the steps of:
a) reacting an amine-comprising compound having n equivalents of amine moieties and an auxiliary amine having nxe2x80x2 equivalents of amine moieties with n+nxe2x80x2 equivalents of a sulfation precursor to form n+nxe2x80x2 equivalents of sulfating species, and wherein said amine-comprising compound further comprises m hydroxyl moieties; and
b) forming m or less sulfated hydroxyl moieties.
These and other objects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (xc2x0C.) unless otherwise specified. All documents cited are in relevant part, incorporated herein by reference.
The present invention relates to a process for sulfating hydroxyl moieties. The process of the present invention in the most general view is a trans-sulfation process comprising a step which forms a sulfating species and a step which provides controllable sulfation of one or more hydroxyl moieties.
Importantly, the process of the present invention can be used to selectively and controllably sulfate the hydroxyl moieties which terminate alkoxylated or polyalkoxylated units, inter alia, alcohols, polyols, saccharides, amines, and polyamines, including polyalkyleneimines. The process of the present invention is especially adaptable to compounds which comprise one or more tertiary nitrogens said nitrogens to be subsequently quaternized.
For the purposes of the present invention the term xe2x80x9chydroxyl-comprising compoundxe2x80x9d is defined herein as xe2x80x9cany organic or inorganic compound having a hydroxyl moiety, xe2x80x94OH, which is capable of being sulfated by the process of the present invention.xe2x80x9d Preferably the xe2x80x9chydroxyl-comprising compoundxe2x80x9d is a compound which is the compound to be sulfated.
For the purposes of the present invention the term xe2x80x9camine-comprising compoundxe2x80x9d is defined herein as xe2x80x9cany organic or inorganic compound having at least one un-oxidized nitrogen, for example, a nitrogen which is not an N-oxide nitrogen, which is capable of accepting an R1 unit as defined herein below and thereby generating a sulfating species as described herein below.xe2x80x9d
For the purposes of the present invention the terms xe2x80x9csulfation precursorxe2x80x9d and xe2x80x9csulfating speciesxe2x80x9d are used interchangeably and are taken to mean a reagent as defined herein below which when reacted in step (a) of the present process forms a chemically reactive species, xe2x80x9csulfation speciesxe2x80x9d, which further reacts to sulfate hydroxyl moieties.
The first required step of the present process, Step (a), is conducted under non-acidic conditions. The second required step of the present process, Step (b), is conducted under acidic conditions.
The following describes the required steps of the present process.
Step (a): Formation of a xe2x80x9csulfating speciesxe2x80x9d. Formation of a sulfating species is the first required step of the process of the present invention.
In a preferred embodiment of the present invention, one equivalent of a sulfation precursor (sulfating agent) is reacted with one tertiary amine moiety to form one equivalent of a sulfating species. In a second embodiment of the present invention, one equivalent of a sulfation precursor is reacted with one amine moiety to form one equivalent of a sulfating species.
In another embodiment of the present invention, up to two equivalents of a sulfating agent is reacted with one secondary amine moiety to form, up to two equivalents of sulfating species. In yet another embodiment, up to three equivalents of sulfating agent is reacted with one primary amine moiety to form up to three equivalents of sulfating species. In the case where a non-tertiary amine is being alkylated multiple times, it is preferred to provide adequate basicity such that unprotonated amine sites remain available for the alkylation steps. The artisan will understand that when a non-tertiary amine moiety is being used, which can be alkylated multiple times with formation of multiple equivalents of sulfation species, the artisan may choose to conduct the process stepwise alternating the alkylation and sulfation steps to achieve the desired level of sulfation.
If desired the process of the present invention may be conducted in the presence of a solvent, preferably non-reactive solvents, inter alia, glyme, diglyme, are used.
In a preferred embodiment of the present invention, wherein a tertiary amine is employed to form the sulfation species, the products which are formed in Step (a) are one equivalent of a sulfating species and one equivalent of a quaternary ammonium compound, an example of which is depicted in the general scheme: 
wherein the amine may (optionally comprise more than one tertiary amino moiety.
Non-limiting examples of tertiary amines include trimethyl amine, triethyl amine, tripropyl amine, tributyl amine, N-alkyl piperidine, N,N-dialkyl piperazine, N-alkyl morpholine, N-alkyl pyrrolidine, N,N,Nxe2x80x2,Nxe2x80x2-tetraalkyl alkylenediamines, N-alkyl polyalkyleneamines, N-alkyl polyalkyleneimines, polyalkyleneimines, and mixtures thereof.
The preferred sulfation precursors according to the present invention have the formula: 
wherein R1 is C1-C22 alkyl, C7-C22 alkylenearyl, and mixtures thereof; preferably R1 is methyl, ethyl, propyl, butyl, benzyl, and mixtures thereof; more preferably methyl. In certain embodiments of the present invention, one R1 is an alkylbenzyl moiety and the other is methyl.
A non-limiting example of Step (a) according to the present invention, is the formation of a sulfating species comprising the step of reacting one equivalent of a tertiary amine which includes the target hydroxyl to be sulfated with one equivalent of a sulfation precursor is represented by the scheme: 
The following example of the formation of a sulfating species comprising the step of reacting one equivalent of a tertiary amine that does not include a sulfatable hydroxyl with one equivalent of a sulfation precursor is represented by the scheme: 
wherein N,N-dimethyl morpholine quaternary ammonium salt is formed and CH3OSO3xe2x88x92 is the sulfating species.
The following is an example wherein the molecule which provides the source of tertiary amine comprises more than one tertiary amine moieties: 
and wherein two equivalents of a sulfating species can be formed per molecule of tertiary amine-comprising compound employed.
In another embodiment of Step(a) of the present invention, a non-tertiary amine is reacted with a sulfation precursor to form an alkylated amine and a sulfating species according to the scheme: 
Step (a) of the process of the present invention is conducted under basic or non-acidic conditions at a temperature of from about 0xc2x0 C. to about 200xc2x0 C. The reaction when exothermic can be controlled by any suitable means, inter alia, cooling the reaction vessel, providing a reflux condenser.
When the hydroxyl moiety comprising compound which is to be sulfated also comprises an amine unit which the formulator does not wish to be affected during the trans-sulfation process, the formulator may add an auxiliary amine, preferably in excess of the stoichiometric amount required. Auxiliary amines may be used when the number of amine units in the hydroxyl moiety comprising compound has an insufficient number of amine moieties to successfully sulfate each hydroxyl moiety.
Step (b): Trans-sulfation step. The formation of a sulfated hydroxyl species is the second required step of the process of the present invention. One equivalent of a sulfating species is required per hydroxyl moiety which is to be sulfated. The products which are formed in Step (b) of the present invention can be depicted by the general scheme: 
wherein said sulfated alcohol (hydroxyl moiety) can be isolated as a zwitterionic species especially when the alcohol to be sulfated serves as the source of nitrogen. The product of sulfation can be isolated as, the protonated species ROSO3H, or a salt ROSO3M. M can be any suitable salt forming cation, preferably, ammonium, lithium, sodium, potassium, magnesium, calcium, barium, and mixtures thereof; more preferably sodium or the ammonium cation which was the counter ion of the sulfating species.
Step (b), which must be conducted under acidic conditions, can employ any suitable acid, inter alia, sulfuric acid, hydrochloric acid, methanesulfonic acid, or Lewis acids, inter alia, boron trifluoride.
The acid catalyst can be added in any amount sufficient to form the desired product, however, the process of the present invention is conducted at a pH less than about 6, preferably less than about 4.5, more preferably less than about 3, most preferably Step (b) is conducted at a pH less than about 2. If fact, acid level of from about 0.01 molar to 1 molar are preferred.
The acid catalyst can be introduced by any manner which is convenient to the formulator, however, good mixing should be utilized. Alternatively, the acid may be generated in situ by adding excess sulfating agent and allowing this excess agent to react with a limited source of proton, inter alia, water. Unreacted alcohol units (under circumstances wherein not all xe2x80x94OH units are to be sulfated) can be carried over into Step (b) from Step (a).
Step (b) of the process of the present invention is conducted at a temperature of from about 0xc2x0 C. to about 200xc2x0 C. The reaction when exothermic can be controlled by any suitable means, inter alia, cooling the reaction vessel, providing a reflux condenser.
One aspect of Step (b) can be used by the formulator to help drive the reaction to completion or to control the level of sulfation. For example, as depicted in the following scheme wherein dimethyl sulfate is used in Step (a) as the sulfation precursor: 
methanol is a by-product of the trans-sulfation step, Step (b). The formulator can remove the methanol as it is formed to drive the reaction to completion. In fact, the relative amount of alcohol by-product which is present can be used as a tool to control the extent of trans-sulfation. However, any alcohol, R1OH which is formed during Step (b) can be removed by any process which is convenient to the formulator, for example, absorption into a molecular sieve (zeolite), crystallization, precipitation, etc. In many instances, removal of the by-product alcohol during the reaction will be preferred. A preferred method for removal is by volatilization.